Flame retardant

Definition:

A flame retardant is a chemical substance that is added to materials during
their manufacturing process in order to both reduce the likelihood of the
finished product catching fire and slow down combustion.

Source: GreenFacts

More:

Since the term “flame retardant” describes a function and not a chemical
class, there is a wide range of different chemicals which are used for this
purpose. Often they are applied in combinations. This variety of products is
necessary, because the materials and products which are to be rendered fire safe
are very different in nature and composition. For example, plastics have a wide
range of mechanical and chemical properties and differ in combustion behaviour.
Therefore, they need to be matched to the appropriate flame retardants in order
to retain key material functionalities.